1. Field of the Invention
The present invention relates, in general, to the field of bath systems for processing semiconductor wafers and, in particular, to bath systems using sonic energy for processing semiconductor wafers.
2. Description of the Related Art
In conventional bath systems for processing semiconductor wafers, a container is loaded with a cassette of semiconductor wafers and a processing liquid (e.g., a solvent, basic solution, acidic solution or distilled water) is circulated through the container. A development in such bath systems has been the use of sonic transducers to direct sonic energy through the processing liquid and to the semiconductor wafers. This use of sonic energy has been found to not only deliver kinetic energy for xe2x80x9cscrubbingxe2x80x9d particles from the surfaces of the semiconductor wafers, but to also facilitate desired chemical reactions at the interface between the surface of the semiconductor wafer and the processing liquid.
Conventional bath systems using sonic energy have not, however, had optimal performance. Due to the location of sonic transducers, some conventional bath systems have been inefficient and non-uniform in their delivery of sonic energy to the semiconductor wafers. For example, the presence of a semiconductor wafer cassette in the container can result in a xe2x80x9cshadowingxe2x80x9d effect where the sonic energy is blocked by cassette support rods from reaching some portions of the semiconductor wafers. Inefficient and non-uniform delivery of sonic energy is worsened when semiconductor wafers of a large diameter (e.g., 300 mm diameter), and thus large area, are placed in the cassette to be cleaned. Furthermore, conventional bath systems typically employ only one generator to power the sonic transducers. Bath systems with a single generator, however, are limited in their ability to power the sonic transducers in a manner that optimizes sonic energy delivery.
Costs are always of concern in semiconductor device fabrication. For such fabrication, several bath systems are typically installed and utilized, each of which can contain different processing liquids. The purchasing cost of several bath systems and the cost of the processing liquids for multiple bath systems can be a significant expense.
Still needed in the field is a bath system for processing semiconductor wafers that provides for the efficient and uniform delivery of sonic energy to the semiconductor wafers. In addition, the bath system should minimize processing time and thus reduce the required number of bath systems, as well as the volume of processing liquid.
The present invention provides a bath system for processing semiconductor wafers with an efficient and uniform delivery of sonic energy to the semiconductor wafers. The bath system minimizes processing time and thus reduces the required number of bath systems, as well as the volume of processing liquid.
The bath system according to one exemplary embodiment of the present invention includes a container (e.g., a quartz container) configured for receiving semiconductor wafers (e.g., a 300 mm diameter semiconductor wafer) and holding processing liquid. The container has two vertical sidewalls and two angled walls, with each of the angled walls being disposed below one of the vertical sidewalls. The bath system includes at least one sonic transducer attached to each of the vertical sidewalls, as well as at least one sonic transducer attached to each of the angled walls. These sonic transducers are arranged so that sonic energy emanating therefrom is directed across the semiconductor wafers during processing. Placement of the sonic transducers on the angles walls is further designed to reduce the xe2x80x9cshadowingxe2x80x9d effect otherwise present in the conventional bath systems.
A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings.